Bolt head marking device



Oct. 14, 1969 s. G. DUNLAP ETAL 3,472,102

BOLT HEAD MARKING DEVICE Filed March 9, 1967 5 Sheets-Sheet l 3 Sheets-Sheet 1 10 v 5 I7. I g

| A3 Q. :E 1-5-1- 24 s Il l6 4, 1969 s. s. DUNLAP ETAL 7 BOLT HEAD MARKING DEVICE Filed March 9, 1967 I 3 Sheets-Sheet 2 INVESTORS SAMU EL 6. DU NLAP SASHA KDMSA W w-w 7 ATTORNEYS Ocli- 14, 1959 s. G. DUNLAP ETAL 3, 7 02 BOLT HEAD MARKING DEVICE Filed March 9, 1967 3 Sheets-Sheet 5 ACTUATING ll7 CIRCUIT ACTUATING MEANS INVENTORS SAMUEL G DU NLAP SASHA KOMSA v" w m I United States Patent 3,472,102 BOLT HEAD MARKING DEVICE Samuel G. Dunlap, Goodfield, and Sasha Komsa, Washington, 11]., assignors to Caterpillar Tractor 'Co., Peoria, 111., a corporation of California Filed Mar. 9, 1967, Ser. No. 621,804 Int. Cl. B25b 13/48, 23/14 US. Cl. 81-53 3 Claims ABSTRACT OF THE DISCLOSURE Apparatus for applying a predetermined torque force to a rotatable fastening member and marking the member to indicate completed application of the predetermined torque force. Driving means adaptable to apply a predetermined torque force to a rotatable fastening member and marking means operable from normally nonmarking relation with the member to marking relation therewith upon application of the predetermined torque force to the rotatable fastening member.

Background of the invention In the use of torque wrenches for applying preselected torques to bolts, nuts and the like in mechanical assemblies such as engine heads or connecting rods, it is desirable to apply a mark to each bolt which has been tightened. The assembler can thus ascertain whether any bolts have been missed and save time by eliminating retightening of any bolts.

Typical prior art torque wrenches applied a mark, e.g., of ink or paint, simultaneously with the engaging of the bolt or nut. By this technique, however, the bolt would be improperly marked if, e.g., the tightening operation were interrupted prior to application of full tightening torque. Further, an ink or paint mark is susceptible of being covered by subsequent painting and elimination of any indication of torque application.

Summary of the invention The present invention provides a torque wrench for applying a predetermined torque force to a rotatable fastening member, such as a bolt or nut, and means for marking the member only upon complete application of the predetermined torque force to the rotatable member by the wrench.

Brief description of the drawing FIGURE 1 is a view in elevation with parts in section of a preferred embodiment of the present invention.

FIGURE 2 is a central vertically sectioned view of the torque wrench of FIGURE 1.

FIGURE 3 is a fragmentary view of the marking end and projection of the marking member shown in FIG- URE 2.

FIGURE 4 is a sectioned view in elevation of an alternate embodiment of the present torque wrench.

FIGURE 5 is a development illustration of a torque wrench shaft surface of the alternate embodiment showing a compensating arrangement of strain gauges disposed thereon.

FIGURE 6 is a schematic illustration of a Wheatstone bridge circuit with the strain gauges of FIGURE 5 as resistor legs therein, an actuating circuit and solenoid actuated thereby.

Description of the preferred embodiment Referring to FIGURES l and 2, torque wrench 10 comprises a lever 11 by which torque force is applied 3,472,102 Patented Oct. 14, 1969 through variable slip clutch assembly 12, torque wrench shaft 13 and female socket 14 to apply a clockwise torque force and thereby tighten rotatable fastening member 15, e.g., a machine bolt disposed in structure 16.

Slip clutch assembly 12, includes a driving collar 17, to which lever 11 is attached, and which is disposed to rotate freely on shaft 13 while resting on retaining means 18. Sawtooth surface 19 of driving collar 17 meshes with sawtooth surface 21 of slip collar 22 in rotational driving relation thereto. Slip collar 22 is also in rotational driving relation with shaft 13 but is free to move longitudinally thereon. Slip collar 22 is further held in rotational driving relation with driving collar 17 by compression spring 23 which interacts between slip collar 22 and a longitudinally variable retaining means 24. Adjusting nuts 26, threadedly engaging shaft 13, control the position of variable retaining means 24 and thus the amount of longitudinal force applied to slip collar 22 of clutch assembly 12 by spring 23. Thus, slip clutch assembly 12 will permit application of a certain maximum torque force to bolt 15 whereupon sawtooth surface 21 of slip collar 22 rides over sawtooth surface 19 of driving collar 17 to terminate torque transmission. Further, the maximum applied torque force may be varied by changing the location of adjusting nuts 26 and, accordingly, the longitudinal force with which spring 23 acts against slip collar 22.

To apply a mark on rotatable member 15 upon complete application of a preselected torque force thereto, marking means 27 is preferably a rod located in an axially disposed cylindrical chamber 28 defined by shaft 13. Except upon complete application of a preselected torque force by wrench 10 to member 15, marking rod 27 is held in spaced apart relation, i.e., non-marking relation, with member 15 by compression spring 29 disposed and interacting between head 31 of marking rod 27 and annular ledge 22 of chamber 28.

With reference also to FIGURE 3, marking end 33 of marking rod 27 is communicable with bolt head 15. To mark bolt head 15 with an identation which will not be subsequently obliterated, e.g., by paint, marking rod end 33 includes a conical marking projection 34 which makes an indentation on bolt head 15 when forced thereagainst. Preferably, marking projection 34 is offset with respect to the axis 36 of rod 27, chamber 28 and thus bolt head 15. Thus, if bolt head 15 is retorqued, as on disassembly and reassembly of structure 16, the probability is high that marking projection 34 will leave a second mark, distinct from a first mark, as an indication that retorquing of bolt 15 is completed.

To operate marking means 27, a pin 37 projects radially inward from slip collar 22 into chamber 28 through a shaft port 38 and has a flattened portion 39 resting atop marking rod head 31.

In marking operation, bolt head 15 is rotated by lever -11 through slip clutch 12 and shaft 13. Upon application of a preselected maximum torque, rotational resistance of bolt 15 causes sawtooth surface 21 of slip collar 22 to ride up on driving collar sawtooth surface 19. Pin 37, being connected to slip collar 22, also rides up, and spring 29 maintains marking rod head 31 in contact therewith. As slip collar teeth 21 ride over driving collar teeth 19 and snap down by the force of spring 23, pin 37 acts against marking rod head 31 to drive marking rod 27 downward. The inertial energy of rod 27 continues its downward motion whereby projection 34 is caused to impinge and indent bolt head 15 and then return to its normal spaced apart relation to bolt head 15 by the action of spring 29. By employing inertial energy of marking rod 27 rather than continued driving force of pin 37, there is less tendency for wrench 10 to jump off bolt head 15 before a mark is applied.

Thus, the above embodiment provides a simple and reliable torque Wrench suitable to apply a preselected torque force to a fastening member without overtorquing. Marking means apply a preferably permanent indentation in the fastening member only upon complete application thereto of a preselected torque force without external power being required for marking operation. Further, the torque wrench 10 is adaptable for electrically powered operation as an impact wrench as well as manual operation through lever 11.

Referring to FIGURES 4, and 6, torque wrench 110 comprises a lever 111 for applying rotational torque force to a rotatable fastening member 112 through a shaft 113 and female socket 114 thereon. Transducing means 116 associated with shaft 113 generates an electrical signal representative of the torque force applied to rotatable member 112. Circuit means 117 receives the representative signal from transducing means 116 and generates an actuating signal when the representative signal corresponds to a preselected maximum torque. Actuating means 118 is disposed to receive said actuating signal and thereupon operate marking means 119 to mark rotatable fastening member 112.

To detect the amount of torque applied to bolt head 112 through shaft 113, transducer means 116 comprises resistive strain gauges 121 disposed upon the surface 122 of a portion 123 of shaft 113 having a uniform cylindrical configuration. Preferably, there are four strain gauges 121 disposed in usual compensating fashion upon shaft surface 122 to eliminate transduction effects in transducer 116 caused by temperature variations or bending of shaft portion 123. Thus, the net resistive transducing effect of strain gauges 121 preferably varies only according to the torque force applied through shaft portion 123 to rotatable fastening member 112 disposed in structure 124. Four terminals, e.g., 126, are insulated with respect to shaft 113 and are electrically connected with strain gauges 121 to provide the Wheatstone bridge arrangement 127 of FIGURE 6. When torque force is applied through shaft portion 123, an electrical signal proportional to the applied torque force is generated at terminals 128 and 129 of Wheatstone bridge 127 and fed to actuating circuit 117 by electrical connectors 131 and 132. Actuating circuit means 117 may be a voltmeter having an adjustable needle contact point whereupon contact of the needle with the contact point generates an actuating signal. Preferably, circuit means 117 is an AC voltmeter, including a suitable holding circuit employed without a phase detector but with an AC base signal applied to Wheatstone bridge 127, to permit generation of a temporary actuating signal when a preselected torque force is applied through shaft 113 is either clockwise or counterclockwise fashion. Alternatively, circuit 117 may be a comparator circuit wherein an actuating signal is generated when the proportional signal from Wheatstone bridge 127 exceeds an adjustable base signal.

Actuating means 118 preferably is a toroidal solenoid defining a cavity 133 disposed in axial alignment atop torque wrench shaft 113. Solenoid 118 is connected to circuit 117 to receive and be actuated by the actuating signal thereon.

Marking means 119, operated by solenoid 118 is preferably a rod with a marking end 134 similar to that shown in and described above with reference to FIGURE 3. Marking rod 119 is disposed in an axial cylindrical chamber defined by shaft 113. Other than when solenoid 118 is actuated, rod 119 is spaced apart from bolt head 112 by a compression spring 136 acting against an enlarged head 137 of rod 119 and chamber ledge 138. Marking rod head 137 extends upward through solenoid cavity 133 and has stop 139 capable of acting against solenoid 118 but not of interfering with marking impingement of marking projection 141 against bolt head 112.

When torque wrench 110 is employed to torque a bolt 112 and apply a mark on completed application of a preelected maximum torque, torque force is applied to bolt 112 and apply a mark on completed application of a preof bolt 112 causes rotational strain in shaft 113. Transducer 116 generates an electrical signal, proportional to shaft rotational strain and applied torque force at terminals 128 and 129 which is fed to circuit 117. When the proportional signal represents a preselected maximum torque force applied to bolt 112, circuit 117 transmits a temporary actuating signal to solenoid 118. Actuation of solenoid 118 sets up a force field in cavity 133 which drives marking rod 119 downward, overcoming spring 136, and causing marking projection to impinge and indent bolt head 112 as an indication of completed up plication of a preselected torque application thereto. When the temporary actuating signal from circuit 117 terminates and solenoid 118 is deactuated, spring 136 again moves marking means 119 into non-marking relation with bolt head 112. Application of torque force to bolt head 112 may be terminated by a slip clutch assembly according to FIGURE 1 or by the operator on operation of marking means 119 or a separate alarm signal actuated by circuit 117.

Thus, the above alternate embodiment provides a torque wrench with electrically actuated marking means to mark a rotatable fastening member only upon application of a preselected torque force thereto. Reliable and broad usage is assured since the Wrench will function in either clockwise or counterclockwise fashion to a maximum torque force which may readily be varied. Further, the absence of moving parts in the transducer means 116 and the nature of strain gauges 12 permits a more accurate and consistent measurement of torque strain in the torque wrench shaft.

The present invention further provides a permanent mark on a rotatable fastening member to indicate completed application of a preselected maximum torque thereto. Thus, proper torquing of specific bolts, nuts. etc., can be ascertained by visual check with the possibility of eliminating the use of expensive castled nuts and cotter pins.

What is claimed is:

1. A torque wrench for applying a predetermined maximum torque force to a rotatable member and thereafter marking the member to indicate completed application of the predetermined torque force, comprismg:

a shaft formed to receive the member in rotatable relation,

means associated with the shaft for rotating the shaft and member,

transducer means disposed upon the shaft between the member and rotating means to detect torque strain therein and generate a proportional electrical signal,

circuit means arranged to receive the proportional signal from the transducer means and generate an actuating signal when the proportional signal indicates torque strain in the shaft equivalent to the preselected torque force,

marking means disposed in the shaft adjacent the member, and

means responsive to the actuating signal from the circuit means for causing the marking means to act upon the rotatable member.

2. The invention of claim 1 wherein the transducer means comprises a compensating arrangement of strain gauges on a surface of the shaft, the strain gauges being electrically connected in a Wheatstone bridge arrangement.

3. The invention of claim 1 wherein the marking means is a rod reciprocably mounted in a bore axially formed through the shaft, an end of the rod adjacent the rotatable member forming a marking configuration, spring means tending to urge the rod out of marking rela- 5 6 tion with the member, and the signal responsive means 3,009,371 11/1961 Hines et a1 81S3 is a solenoid disposed adjacent the marking rod. 3,389,623 6/1968 Gill 8152 References Cited JAMES L. JONES, JR., Primary Examiner UNITED STATES PATENTS 5 Us CL X'K 1,985,916 1/1935 Coates et a]. 8152 2,795,131 6/1957 Booth 71 1 73-139;8152-5173"12,46

2,943,480 7/1960 Nelting 73136X 

